Tuesday, 11 February 2014

Wacom Graphics Tablet from broken HP TX2000 tablet PC

Next Steps
  • LVDS to VGA boards have become more common since I originally did this project, I might get one and turn it into a complete external touchscreen monitor
Version 1
I acquired one of these laptops after it malfunctioned. Apparently this is a known issue of overheating.
I initially tried to fix it by reseating the graphics chip, which worked for a while, however it quickly began to malfunction again.

So I tore it apart to see if there was anything useful I could scavenge.

It's well documented that laptop screens are near-impossible to get working as standalone monitors, due to the differences in the way they communicate with the computer compared to regular screens, so instead I set about trying to make the touch screen work as a standalone tablet.

I was expecting this to be quite difficult. Turns it it's one of the easiest hacks I've ever done.

There's a 9 pin connector that connects the digitizer. In amongst those 9 pins, there's USB pins. (see this forum post for pinout image).

It's not a simple case of soldering on a full USB plug though, the tablet works at a lower voltage (3.3v) than the standard 5V.

To overcome this, putting 3 N4148 diodes on the voltage line was sufficient to drop the power to a usable level. This isn't an exact measurement, but it works.

A standard Fedora 16 desktop install comes with wacom drivers pre-installed, so the software side of things was basically plug-and-play. The only change I made was to change the pen mapping from absolute to relative, which was better suited to my monitor setup.

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